The invention relates to a dental handpiece comprising an end grip member or handle to be gripped by a user and which contains a motor to which leads a propellant air line the flow to which is controlled by means of an adjusting ring mounted on the end grip member, and a headpiece which can be removably attached by way of a neck piece to the end grip member and which carries a rotating tool.
Such handpieces are known, for example, from AT-A-347 013 and DE 30 09 337. The motor disposed in the end grip member is designed as a pneumatic motor and includes blades, a sleeve-shaped housing forming a stator, and a rotor which is located in the housing and having an axis of rotation extending parallel to an axis of a circular cylindrical inner wall of the housing and offset relative thereto. At least one air inlet port for compressed air and at least one air outlet port open into a space between the rotor and the circular cylindrical inner wall. When compressed air is admitted into the motor, the compressed air flows through the air inlet port(s) into the space between rotor and circular cylindrical inner wall and pushes in front of it a blade that projects the furthest beyond the rotor, so that the rotor begins to rotate, and then the next blade is impinged on by the compressed air.
A range of velocity that can be obtained with such a device lies between 0 and 40,000 rpm, for which the technical term is the low speed range. A desired speed is set by means of an adjusting ring, which, starting from a zero position, can be set to different fast clockwise rotation or to counter-clockwise rotation positions. For higher speeds, either a mechanical drive or a turbine with an air drive, which immediately envelope the rotating tool (cf. AT-A 344 875) is used conventionally. Such turbines are to be operated in a speed range of 200-350,000 rpm.
According to the current state of the art, if a change is made from a handpiece with a drive in the end grip member to a handpiece with head turbine, the end grip member is changed. This means not only a certain time-consuming manipulation, but also increased costs due to a larger number of end grip members that must be kept on hand.